It is known in the electrical field that air dehydrating breathers are used in connection with electrical devices having oil expansion vessels, such as power transformers, on load tap changers, chokes, etc.
These oil-expansion vessels, which are constituted, for example, by oil conservators in the case of power transformers, have the function of compensating for the unavoidable volume changes of insulating oil used in such electrical devices, which volume changes result from temperature fluctuations. To this end, oil expansion vessels are supplied with air previously treated in a suitable air breather, also indicated as dryer or demoisturizer or dehumidifier or similar terms, so as to eliminate or drastically reduce its humidity, in order to prevent a reduction of the breakdown voltage of the insulating oil.
According to known solutions, an air breather includes a tank inside which there is an air absorbing agent which removes humidity from the air entering into the tank. Then, the dehumidified air is routed into the oil expansion vessel of an associated power electrical device.
The humidity absorbing agents can be divided in general in two groups: those which cannot be regenerated and exhaust their absorbing capabilities after a certain working life, for examples zeolites, and hence must be replaced sooner or later; and those instead, such as silica gels, which can be regenerated at least for a certain number of times.
WO 2005/055255 discloses, for example, an air dehydrating assembly of a known type, in which a dehumidifying tank has an inlet for the air to be dehumidified, an outlet for dehumidified air, and moisture absorption means consisting of a plurality of granules or salts that can be thermally regenerated and are suitable to dehumidify air coming from outside.
Another example of an air demoisturizer for oil-insulated transformers, chokes, and tap changers with a heat-regenerable absorbent is disclosed in U.S. Pat. No. 6,709,496.
Although known air breathers perform their basic functions in a quite satisfying way, there is still a desire and room for further improvements, such as with regard to their flexibility of use, especially when there are more oil expansion vessels used in the same electrical device or power application.
Exemplary embodiments of the present disclosure fulfil this desire by providing an air dehydrating breather assembly and a method for dehumidifying air suitable to be supplied into oil expansion vessels of power electrical devices as described hereinafter.